<!DOCTYPE html>
<html lang="zh-CN">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>
  <script>
    switch (3) {
      case 1:
        console.log("1");
        break
      case 2:
        console.log("2");
        break
      case 3:
        console.log("3");
        break
      default:
        console.log('没有符合条件的');
        break
    }
  </script>
</body>

</html>